In a pivot bearing of this type, a plurality of ball bearings are conventionally located axially (in a tandem manner) with respect to a shaft conforming to inner rings of the ball bearings, thus allowing a swing motion around the shaft with high precision and at low torque. Meanwhile, a pivot bearing is often used as a bearing for a swing arm (swing motion) type head access mechanism in a magnetic recording apparatus such as in a hard disk drive (hereinafter denoted by the acronym “HDD”) in particular. In an HDD, an areal recording density is continually increased and is now about to reach 1 Tbpsi (1 Tera Bit Per Square Inch) due to increases in linear recording density and track density. Hence, a desire for precision of micro-positioning is also growing, and there is an increasing demand for higher precision of a pivot bearing.
According to Patent Literature 1, an inner ring of one of two bearings included in a pivot bearing is formed at a pivot shaft, thus making it possible to reduce the number of components and torque variations. Moreover, Patent Literature 1 discloses fixation of an arm of an HDD and the pivot bearing via a tolerance ring. Patent Literature 1 further discloses that the tolerance ring is located in a gap between an arm hole and the pivot bearing, and is thus compressed to exert a reaction force so that the pivot bearing can be elastically supported with respect to the arm hole. Furthermore, Patent Literature 2 discloses that when a pivot bearing is fixed in an arm hole via a tolerance ring, protruded portions (projections) of the tolerance ring are plastically deformed, thereby reducing a stress applied to an outer ring of the pivot bearing, reducing the influence associated with deformation of the outer ring, and obtaining a higher removing force. Besides, Patent Literature 2 also discloses that an allowable range of variations in a gap between the arm hole and an outer diameter of the pivot bearing can be increased, and an increase in torque can be prevented in a state where the pivot bearing is mounted.